The application of trace element geochemistry to determine the provenance of soapstone vessels from Dorset Palaeoeskimo sites in western Newfoundland

O'Driscoll, Cynthia Marie (2003) The application of trace element geochemistry to determine the provenance of soapstone vessels from Dorset Palaeoeskimo sites in western Newfoundland. Masters thesis, Memorial University of Newfoundland.

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Abstract

Petrography and trace element geochemistry are used to characterise Dorset Palaeoeskimo (ca. 2000-1200 B.P.) soapstone artifacts from five sites in Western Newfoundland. Soapstone artifacts were collected from Cape Ray, Englee, Fleur de Lys, Pittman, and Port au Choix sites, and their mineralogy and trace element abundances are compared to outcrop samples from Bear Cove Road, Fleur de Lys, St. Anthony, Straitsview, Tablelands and Trout River. Complementary analytical techniques were used to characterise all forty-four samples. Petrographic analysis was supplemented by x-ray diffraction analysis to identify mineralogy, major element determinations were made by x- ray fluorescence, and trace elements were determined using inductively coupled plasma- mass spectrometry. -- Immobile or alteration resistant elements are the most useful elements for determining provenance. For this study, these are the rare earth elements (REE) and the high field strength elements niobium and thorium. The REEs are a coherent group of elements and exhibit certain behaviours as a group. Differences in the REE chemistry of samples are based on REE abundances, the shape of the REE patterns and the slopes of the REE pattern when plotted on a log-scale plot where concentrations of these elements are normalised to standard values for primitive mantle. Definite differences exist between REE abundances in the tested samples. There are however, consistent thorium and light rare earth element enrichments, and a negative niobium anomaly in most artifacts, and in the Tablelands and Trout River outcrop samples. Patterns are characterised as U-shaped, L-shaped, or linear. -- It is possible to define sub-populations of artifacts based on individual and group rare earth element concentrations and patterns. Sample populations from the Fleur de Lys outcrop match artifacts collected at Englee, Fleur de Lys, and the Pittman site suggesting Dorset groups at these sites collected rocks at the Fleur de Lys quarry. The artifacts from Cape Ray and Port au Choix have not been significantly carbonatised and have higher concentrations of aluminium represented as chlorite in thin section, and only 10-15% carbonate (i.e., magnesite). However, Cape Ray and Port au Choix artifacts have significant differences in REE (especially heavy rare earth elements) abundances and their different shaped REE patterns suggest different outcrop sources. This differs from the significantly carbonatised (i.e., 40-50% magnesite in thin section) artifacts from Englee, Fleur de Lys, and the Pittman site. These artifacts exhibit more intensive alteration and have similarly shaped REE patterns and abundances. -- Of the outcrop samples tested, only Fleur de Lys is suggested to be a possible source of artifacts. The St. Anthony outcrop (based on enriched heavy REE abundances) is clearly derived from a different mantle source than the Trout River and Tablelands samples, which exhibit enriched Th and have a negative Nb anomaly and very low REE concentrations. The Straitsview outcrop is not of ultramafic composition and is not a source of artifacts studied. -- These data have notable consequences for the distribution of soapstone during the Dorset period in Newfoundland, and support Douglas Robbins's theory, which states that three regional cultural variants of the Dorset culture occur in Newfoundland; the west coast (e.g., Port au Choix), northwest coast (e.g., Fleur de Lys, Pittman, and Englee sites) and south coast (e.g.. Cape Ray) variants. This hypothesis is based on the idea that the Dorset utilised the local raw materials within these particular regions.

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